1. Technical Field
The present invention relates to a thermal detector, a thermal detection device, an electronic instrument, and a thermal detector manufacturing method.
2. Related Art
Thermal detection devices are known as light sensors. Thermal detectors absorb light that has been emitted from an object in a light-absorbing layer, convert the light to heat, and measure the change in temperature with a heat-detecting element. Thermal detectors include thermopiles that directly detect the increase in temperature accompanying light absorption, pyroelectric-type elements that detect a change in electrical polarity, and bolometers that detect the increase in temperature as a change in resistance. Thermal detectors have a characteristically wide wavelength range over which measurements can be made. In recent years, semiconductor fabrication technologies (e.g., MEMS technologies) have been used, and the production of smaller-scale thermal detectors has been attempted.
In order to increase detection sensitivity and improve response in thermal detectors, it is critical to efficiently transfer the heat that is generated in the light-absorbing layer to the heat-detecting element.
The structure of a heat-detecting element for improving thermal transfer efficiency is described, for example, in Japanese Patent No. 3339276. The infrared detecting element described in Japanese Patent No. 3339276 (herein referred to as a thermopile-type infrared detecting element) has a highly thermally conducting layer that is provided between an infrared light sensing part and an infrared light absorbing layer. Specifically, a membrane is formed over a cavity, and the membrane is supported on the surrounding substrate by protruding beams that are provided at the four corners. The center membrane portion has a highly thermally conducting layer and an infrared light absorbing layer, and the edge portions have thermopile elements. In addition, the highly thermally conducting layer is made from a material having excellent infrared light reflectance, such as aluminum or gold.